Revisiting microbial exopolysaccharides: a biocompatible and sustainable polymeric material for multifaceted biomedical applications

Abstract

Microbial exopolysaccharides (EPS) have gained significant attention as versatile biomolecules with multifarious applications across various sectors. This review explores the valorisation of EPS and its potential impact on diverse sectors, including food, pharmaceuticals, cosmetics, and biotechnology. EPS, secreted by microorganisms, possess unique physicochemical properties, such as high molecular weight, water solubility, and biocompatibility, making them attractive for numerous functional roles. Additionally, EPS exhibit significant bioactivity, contributing to their potential use in pharmaceuticals for drug delivery and tissue engineering applications. Moreover, the eco-friendly and sustainable nature of microbial EPS production aligns with the growing demand for environmentally conscious processes. However, challenges still exist in large-scale production, purification, and regulatory approval for commercial use. Advances in bioprocessing and microbial engineering offer promising solutions to overcome these hurdles. Stringent investigations have concluded EPS as novel sources for sustainable applications that are likely to emerge and develop, further reinforcing the significance of these biopolymers in addressing contemporary societal needs and driving innovation in various industrial sectors. Overall, the microbial EPS represents a thriving field with immense potential for meeting diverse industrial demands and advancing sustainable technologies.

Introduction

In the vast and diverse realm of microorganisms, an intriguing feature of great importance has been discovered—the EPS. EPS, a class of complex carbohydrates generated by a wide range of microorganisms, including bacteria and fungi, are essential to their survival and ability to adapt (Prasad and Purohit 2023). The bacteria excrete these biomolecules (EPS) into the extracellular environment. They are long-chained polymers made up of repeated sugar units. Due of their numerous uses in a variety of industries, including food, medicine, cosmetics, and agriculture, EPS have attracted a lot of interest (Asgher et al. 2021; Nandan et al. 2023). Numerous commercial uses benefit from their distinctive physicochemical qualities, which include their high water-holding capacity, stability, and biocompatibility. Modern microbiology is heavily interested in and exploring these biopolymers since they are essential not only for the survival, biofilm development, and ecological roles of many bacteria but also its exigency in the industrial sectors (Sajna et al. 2021).

A dynamic, complex web of biomolecules called the extracellular matrix (ECM) surrounds and supports microbial cells. Even while ECM is typically thought to only be used by higher species like mammals, it is becoming clear that bacteria also use their own type of the matrix (Sajna et al. 2021; Rana and Upadhyay 2020). Exopolysaccharide-rich microbial ECM acts as a barrier, shielding cells from external stresses and promoting interactions with other species and surfaces. Because of this, the importance of EPS in microbial communities goes beyond only protecting individual cells and includes aiding the stability and resilience of the microbial cells against unfavourable conditions of ecosystem they thrive in. EPS are fascinating research topics because of their enormous diversity and complexity (Ngampuak et al. 2023; Andrew and Jayaraman 2020). Their large range of monomeric sugar compositions, glycosidic connections, and branching patterns produce a variety of EPS structures with different characteristics. The enormous diversity of tasks carried out by EPS-producing bacteria is a result of these structural variances translating into differences in physicochemical properties, such as solubility, viscosity, and elasticity (Tabernero and Cardea 2020). Determining these polymers' functions and prospective uses in a variety of industries, including medicine, food, and pharmacy, requires an understanding of their structural underpinnings. Within microbial cells, exopolysaccharide production is a difficult and strictly controlled process. Specific glycosyltransferases catalyse a sequence of enzymatic processes during biosynthesis that lead to the assembly of sugar monomers into polymer chains. To guarantee optimum EPS synthesis, this process necessitates careful synchronisation of gene expression and metabolic pathways (Tabernero and Cardea 2020). Environmental elements like temperature, pH, and nutrient availability have a big impact on how EPS is made, highlighting how adaptable these microbial polymers are. Understanding the regulatory processes that lead to EPS formation can help us understand how bacteria adapt to changing environmental circumstances. EPS have a wide range of uses that have a significant influence on how bacteria live. The participation of EPS in the production of biofilms is one of its best known functions (Ali et al. 2023; Sajna et al. 2021). Complex microbial communities that are entwined within an EPS matrix and cling to surfaces and host cells are known as biofilms. These communities of microbes can communicate with one another and exchange nutrients more easily when they are in a biofilm. Additionally, EPS can function as a carbon and energy store, assisting in cell survival under nutrient-restrictive circumstances. Additionally, certain EPS have the potential to bind metals, which affects the availability and cycling of metal ions in the environment (Prasad and Purohit 2023).

EPS are desirable targets for a variety of biotechnological applications due to their unique functions (Shukla et al. 2019; Abedfar et al. 2020). EPS can be used as thickeners in cosmetics, stabilisers in the food and pharmaceutical sectors, and even as parts of biodegradable polymers. Furthermore, interest in EPS's potential medicinal uses has grown due to their capacity to influence immunological responses and communicate with host cells. For the future of medicine, EPS-based research has great potential in the areas of medication delivery, immunomodulation, and wound healing (Prasad and Purohit 2023; Nandan et al. 2023). The current review aims to provide a complete understanding and information on microbial EPS and its immense potential application in the field of biomedical sciences.

Reports on exopolysaccharide-producing microorganisms

EPS, one of a wide variety of extracellular compounds produced by microorganisms, the smallest living things on Earth, play a crucial function, not only in the functioning of the microbes but also in its need in the industrial sectors. Numerous microbial species, including bacteria, fungi, and even archaea, produce and release these intricate biopolymers made up of sugar units (Talebi Atouei et al. 2019; Gunasekaran et al. 2022) that have been widely utilized and exploited in the field of biomedical sciences, which has been described comprehensively in Table 1. In addition to being common among microbes, EPS production is also essential for their survival, environment adaption, and interactions with other living things. The interesting world of bacteria that produce EPS is illuminated by this thorough study. Exopolysaccharide-producing microbes exude these polymers into the environment to create an extracellular polymeric substance, or glycocalyx, which serves as a protective matrix (Habib et al. 2022). This EPS matrix protects the microbial cells against a variety of environmental stresses, including as desiccation, temperature changes, and chemical attacks, by acting as a strong and durable barrier (Baruah et al. 2022). This protective matrix also increases the microbial cell's resistance to antimicrobial substances, making it a key component in the emergence of antibiotic resistance. In addition to providing protection, EPS also functions as a matrix, promoting microbial aggregation, adherence to surfaces, and the development of intricate biofilm ecosystems (Cao et al. 2023).

Table 1.

List of various commercially important microbial EPS along with their source and biomedical applications

Microbial EPS	Microbial source	Biomedical applications	References
Alginate	Pseudomonas aeruginosa	Wound healing, drug delivery, tissue engineering	Manna et al. (2023)
Xanthan	Xanthomonas campestris	Thickening agent, stabilizer, emulsifier	Waoo et al. (2023)
Dextran	Leuconostoc mesenteroides	Blood plasma expander, drug delivery, wound healing	Waoo et al. (2023)
Pullulan	Aureobasidium pullulans	Film-forming agent, drug delivery, tissue engineering	Waoo et al. (2023)
Gellan	Sphingomonas paucimobilis	Gelling agent, stabilizer, thickener	Waoo et al. (2023)
Curdlan	Agrobacterium sp.	Antitumor, immunomodulatory, antimicrobial	Latiyan et al. (2023)
Hyaluronic acid	Streptococcus zooepidemicus	Skin rejuvenation, joint lubrication, wound healing	Shukla et al. (2023)
Levan	Zymomonas mobilis	Prebiotic, immunomodulatory, antimicrobial	Domżał-Kędzia et al. (2023)
Succinoglycan	Sinorhizobium meliloti	Plant growth promotion, biofilm formation	Sowani et al. (2023)
Cellulose	Gluconacetobacter	Wound dressing, drug delivery, tissue engineering	Pandey et al. (2023)
β-Glycan	Fusarium proliferatum	Higher reactivity and lower binding affinity compared to imatinib, an oral chemotherapy drug for cancer	Behera et al. (2023)
Mushroom β-glucan	Phellinus linteus	Immunomodulatory, anti-inflammatory, anti-cancer properties	Hu et al. (2023)
Ganoderan	Ganoderma lucidum	Anticancer, immunomodulatory, antioxidant properties	Sułkowska-Ziaja et al. (2023)
Lentinan	Lentinula edodes	Anticancer, immunomodulatory properties	Bernal-Mercado et al. (2023)
Schizophyllan	Schizophyllum commune	Anticancer, immunomodulatory properties	Gou et al. (2023)
Pleuran	Pleurotus ostreatus	Immunomodulatory, anti-inflammatory properties	Zhao et al. (2024)
Fungal pullulan	Aureobasidium pullulans	Antioxidant, anti-inflammatory properties	Saber et al. (2023)
Fungal chitin-glucan	Fomes fomentarius	Antimicrobial, immunomodulatory properties	Kalitukha et al. (2023)
Fungal dextran	Paecilomyces hepiali	Drug delivery systems, wound healing properties	Stoica et al. (2023)
Fungal scleroglucan	Sclerotium rolfsii	Thickening agent, film-forming properties	Stoica et al. (2023)
Xyloglucan	Mesotaenium caldariorum	Wound healing, drug delivery systems	Feng et al. (2023)
Pullulan	Scenedesmus pannonicus	Food industry (thickening agent), drug delivery systems	Ponton et al. (2020)
Chrysolaminarin	Prymnesium parvum	Antioxidant, anticancer properties	Andreeva et al. (2023)

A crucial component of microbial life is represented by biofilms, which are intricate colonies of bacteria enclosed in an EPS matrix. The production of biofilms is started when bacteria adhere to surfaces and start secreting EPS (Bengoa et al. 2021). In comparison to free-living planktonic cells, biofilms have significant benefits, because they provide better protection, increased nutrition availability, and the capacity to resist harsh environmental conditions. In contrast to their planktonic counterparts, microbes living in biofilms have altered gene expression patterns that result in distinctive morphologies and metabolic activities (Mukhtar et al. 2020). In addition to serving as the microbial cells' anchor in biofilms, the EPS matrix encourages complex communication networks that allow for cooperative behaviour and coordinated responses to environmental signals (Lee et al. 2022). EPS generated by several bacteria exhibit an astonishing structural variety. The monomeric sugar content, glycosidic connections, branching patterns, and overall size and form of EPS can all vary. These structural differences, which are frequently strain- or species-specific, provide the EPS special physicochemical features. For instance, while certain EPS are more hydrophobic (e.g., Curdlan) than others, some are very water-soluble (e.g., Pullulan). Some EPS are stiff and crystalline in structure, while others have a slimy and mucoid texture that aids in attachment to surfaces (Srinivash et al. 2023). In order to understand the functions of EPS and prospective applications, it is crucial to comprehend their structural properties. Exopolysaccharide production in bacteria is a closely controlled process. In order to assemble and export EPS precursors, complicated gene–enzyme interactions are necessary (Srinivash et al. 2023). Environmental factors including nutrition availability, oxygen concentrations, temperature, and osmotic pressure can have a big impact on how these EPS biosynthesis genes are expressed. Additionally, the regulation of EPS generation in the context of biofilm growth is greatly influenced by quorum sensing, a complex communication system used by many microbes. It is essential to comprehend the complex regulatory processes governing EPS synthesis in order to manipulate EPS production in a positive manner and perhaps manage biofilm-related problems in industrial and medical contexts (Srinivash et al. 2023).

Microbial sources of exopolysaccharide

EPS as known are released and fabricated by a wide of array of microbes, each of which adds a different structure and function to the extracellular matrix. This diversity of EPS-producing microorganisms includes bacteria, archaea, and fungus and is found in all living forms. EPS are often produced by bacteria, and many different species have been shown to be capable of synthesising EPS for a variety of uses. Xanthomonas campestris, which is known for making xanthan gum, is one such instance. High molecular weight EPS xanthan gum, which is frequently used in the food sector and a variety of industrial items, has exceptional thickening and stabilising qualities (de Souza et al. 2022). Pseudomonas aeruginosa, another well-known bacteria, produces alginate, which is a part of its EPS matrix. Alginate's biocompatibility and moisture-retentive properties make it useful in the biomedical field, notably for tissue engineering and wound dressings. An organised community of microbial cells buried inside a self-produced EPS matrix, known as a biofilm, is primarily related and vital for the survival and stability of the microbes (Gheorghita et al. 2022). For instance, Escherichia coli is known to produce biofilms, and its EPS promotes cell attachment and offers defence against environmental stressors (Öztürk et al. 2023). In contrast, Staphylococcus epidermidis produces biofilms largely on surfaces, and since it helps in the colonisation of indwelling medical devices like catheters, its EPS is associated to infections caused by medical devices. EPS can also be produced by archaea, albeit being less well-studied than bacterial EPS (Le et al. 2019). For instance, the halophilic archaeon Haloferax volcanii generates sulfated EPS that aid in osmo-protection and play a part in adaptation to high-salt conditions. Their fascination and potential biotechnological utility are increased by the fact that these archaeal EPS also display distinctive structural traits that set them apart from bacterial and eukaryotic EPS (Gagliano et al. 2022).

Moulds or filamentous fungi are known for producing EPS, which is important in a variety of ecological and economic applications. For instance, the highly researched fungus Aspergillus niger produces EPS that contains fucose and is used in the food sector as a gelling agent and stabiliser (Asgher et al. 2020). Pullulan, a linear EPS with uses in the creation of biodegradable films and coatings, is another substance produced by Aspergillus niger and Aureobasidium pullulans (Wani et al. 2021). Fucoidan, an EPS that is produced by the fungus Tremella fuciformis, has drawn interest due to its possible biological uses. Fucoidan is a viable candidate for pharmaceutical and nutraceutical development due to its documented antioxidant, anticoagulant, and anticancer effects (Li et al. 2020). A medicinal mushroom called Ganoderma lucidum (Reishi mushroom) creates EPS with a variety of bioactive substances, including beta-glucans. Beta-glucans are being researched for their potential to improve immune responses and as adjuvants in vaccines due to their immunomodulatory qualities (Ahmad et al. 2021).

Lab-scale to industrial production of microbial exopolysaccharides

EPS produced by microorganisms have drawn a lot of attention because of the wide range of sectors they are used in, including food, medicine, biotechnology, and environmental clean-up (Wang et al. 2023a). Both lab-scale and industrial-scale EPS manufacturing are possible, each with its own concerns, difficulties, and benefits. Small-scale bioreactors or flasks are frequently used in the lab for the cultivation of microorganisms for the synthesis of microbial EPS (Zampieri et al. 2023). Selection of the strain is the first step in the procedure since the features of the EPS produced by various microbial species vary. Once the right strain has been selected, it is injected into a nutrient-rich medium that has been tailored to supply the required carbon and energy sources for EPS production. The circumstances of the culture are crucial to the generation of EPS (Xu et al. 2022). To produce the greatest yield of EPS, variables including temperature, pH, dissolved oxygen, agitation rate, and nutrient content must be properly managed (Banerjee et al. 2021). The production phase differs from the growth phase; it is often marked by a decrease in cell growth but an increase in EPS output. Regular sampling and analysis of the culture media are required to track the development of EPS synthesis (Combie and Öner 2023). The EPS synthesis process may be better understood by lab-scale manufacturing, which also enables the improvement of culture conditions. Lab-scale setups are better suited for preliminary research, strain screening, and process optimisation before switching to industrial-scale production since the volumes they can generate are constrained (Bovio-Winkler et al. 2023).

Significant scaling up from lab-scale methods is needed for the generation of microbial EPS in industrial settings (Střížek et al. 2023). High yields and efficient production depend on the kind and size of the bioreactor, the medium composition, and the fermentation conditions. Stirred-tank reactors, airlift reactors, and fermentors are a few examples of the several types of bioreactors that may be used in industrial settings. The decision is made based on the particular microbe, necessary oxygen transfer, and output level (Nataraj et al. 2023). To maximise EPS production, continuous or fed-batch methods are frequently utilised in industrial settings. As the growing medium's composition has a considerable impact on how EPS is synthesised, medium optimisation is a crucial component of industrial production (Tatulli et al. 2023). To attain the required EPS production, nutrient availability, carbon sources, and trace elements must be optimised. Throughout the production process, quality control techniques are used to guarantee repeatability and uniformity (Sarvajith and Nancharaiah 2023). Another key phase in the manufacturing of industrial EPS is downstream processing. It entails removing EPS from the fermentation broth and then purifying, concentrating, and separating it (Wani et al. 2023). To recover the EPS, processes including centrifugation, filtering, and precipitation are used. Additional purification procedures to get rid of contaminants and other components from the EPS can be necessary depending on the final product that is sought (Bisht et al. 2023).

Biosynthetic pathways of exopolysaccharides in microbial systems

Bacteria have both intracellular and external mechanisms for producing EPSs. The Wzx/Wzy-dependent route, the ABC transporter-dependent pathway, the synthase-dependent pathway, and extracellular biosynthesis via sucrase protein are the four key processes involved in EPS production. Figure 1 presents an illustration of these paths. Heteropolysaccharides are often formed utilising the Wzx/Wzy-dependent pathway and the ABC transporter-dependent pathway, whereas homopolysaccharides are typically made using the synthase-based method and extracellular production pathway.

Fig. 1.

Biosynthetic pathways involved in synthesis of microbial EPS (P-Phosphate; GT-Glycosyl transferase; PCP-Polysaccharide Co-polymerase; TPR-Tetratricopeptide repeat protein; OPX-Outer membrane polysaccharide export; GMP-Guanosine monophosphate) (Created using Biorender.com)

The Wzx/Wzy-dependent pathway involves three main stages: (a) synthesis of nucleotide sugars, (b) assembly of repeat units, and (c) polymerization and export. First, sugar residues are actively carried into the cells where they are transformed into different monomeric units. These units are subsequently joined to a C55 lipid carrier at the inner membrane known as undecaprenyl phosphate (Und-P), which serves as an anchor. Glycosyltransferases (GTs) join more sugar units together to create repeating units in the second step. The Wzx flippase then moves these repeating units across the cytoplasmic membrane. The translocated oligosaccharide units are modified by several enzymes, including methylation and acetylation, in the last step before being polymerized into polysaccharides by the Wzy protein. Homopolysaccharides, a term for the polysaccharides produced by the Wzx/Wzy-dependent pathway, display a wide range of sugar units (Dueholm et al. 2023; Rekha et al. 2023). Through ABC transporters, these formed polysaccharides are discharged to the cell surface. Homopolysaccharides including gellan, xanthan, and kefiran are generated by probiotic bacteria through a Wzx/Wzy-dependent pathway. The ABC transporter-dependent process, which requires the transit of active sugar units to the inner membrane where they join with an Und-P molecule to form an Und-PP-sugar molecule. The full-length polysaccharides are produced by certain GTs that are found on the cytoplasmic side of the inner membrane. Then, a tripartite efflux pump complex moves these polysaccharides over the inner membrane. This specific route mainly contributes to the production of capsular polysaccharides (Zhang et al. 2023a; Masselot 2023).

The homopolysaccharides produced by the synthase-dependent route are made up of just one kind of sugar unit, such as bacterial alginate and cellulose. A membrane-embedded synthase/inner membrane transporter known as bacterial cellulose synthesis (BCS) A is used in this process to construct UDP-glucose units. It is crucial to remember that bacterial cellulose synthesis operons can differ significantly from one another and are unique to many bacterial species (Wu 2023; Cifuente et al. 2023). Extracellular sucrase enzymes convert sucrose into monomeric units as part of the extracellular biosynthesis pathway, which takes place beyond the outer cellular membrane. GTs subsequently polymerize these monosaccharide units to create fructan and glucan, both of which have different branching patterns. Glucan sucrases are further divided into alternan sucrases, dextran sucrases, mutan sucrases, and reuteran sucrases inside probiotic bacterial cells. On the other hand, levan sucrases and inulin sucrases are subclasses of fructan sucrases. Therefore, homopolysaccharides are generated by probiotic bacteria through the extracellular biosynthetic route (Duan and Luan 2023).

Characterization techniques of microbial exopolysaccharides

EPS are intricate biopolymers made by microbes with a variety of forms and purposes. Understanding EPS's physicochemical and structural properties is essential for using it in a variety of applications. The first characterisation of EPS relies heavily on spectroscopic methods (Neto et al. 2023). By revealing details about the existence of functional groups like hydroxyls, carbonyls, and sulphates, Fourier Transform Infrared Spectroscopy (FTIR) sheds light on the monosaccharide composition and connections within the EPS. By giving details on the linkage patterns, glycosidic linkages, and anomeric configurations of sugar units in EPS, Nuclear Magnetic Resonance (NMR) spectroscopy, on the other hand, enables extensive study of EPS structures and aids in structural determination (Xu et al. 2023).

The characterisation of EPS makes considerable use of chromatographic methods. The molecular weight and size distribution of EPS are determined using Gel Permeation Chromatography (GPC), which sheds light on their macromolecular structure. The analysis of EPS generated by complex microbial communities, in particular, benefits from the separation and quantification of individual sugar monomers in EPS using Gas Chromatography-Mass Spectroscopy (GC–MS) and High-Performance Liquid Chromatography (HPLC) (Erdem et al. 2023). Visual understandings of EPS structures are provided through microscopy methods. While Transmission Electron Microscopy (TEM) offers finely detailed pictures at the nanoscale, crucial for examining the ultrastructure and internal organisation of EPS, Scanning Electron Microscopy (SEM) permits the analysis of the surface morphology and three-dimensional architecture of EPS (Ahuja et al. 2023). The viscoelastic characteristics of EPS gels are analysed using rheological techniques, including rheometry, and are crucial for comprehending how the gels respond to various stresses. By determining the amount of carbon, hydrogen, nitrogen, and sulphur in EPS, elemental analysis (CHNS) makes it easier to identify their elemental composition and stoichiometry (Zhang et al. 2023c). Gas chromatography–Mass Spectrometry (GC–MS) monosaccharide composition analysis enables the identification and quantification of the sugar monomers present in EPS, giving essential details regarding the monosaccharide composition (Tilwani et al. 2023; Jiang et al. 2023). The surface charge of EPS is also revealed by Zeta Potential Analysis, which is crucial for comprehending the electrostatic interactions between EPS and other components. Combining these numerous characterisation methods provides a thorough grasp of the functioning and complexity of EPS, allowing researchers to fully use their potential in a variety of applications, such as biotechnology and medical areas (Xiao et al. 2023).

Multifarious applications of microbial exopolysaccharides

EPS, which are produced by microbes, have drawn a lot of interest because of their numerous uses in the biological and medical sciences (Saha and Datta 2022). These complex biopolymers have distinct physicochemical characteristics, a wide range of functions, and are useful in a variety of biological and medicinal applications. Applications for tissue engineering and wound healing have showed promise for EPS-based biomaterials (Zaheer 2019). EPS may hasten the healing of wounds by encouraging cell migration, proliferation, and extracellular matrix deposition. Furthermore, dressings with EPS have been designed to provide a moist environment that promotes tissue regeneration. EPS-based scaffolds are excellent options for tissue healing because they act as three-dimensional matrices in tissue engineering that enable cell proliferation and tissue development (Asianezhad et al. 2023). Drug delivery systems with controlled release features can be created using EPS. Drug distribution that is prolonged and targeted is made possible by encapsulating therapeutic chemicals inside EPS matrices. Drugs can be stabilised and protected against deterioration with EPS, guaranteeing maximum bioavailability and therapeutic effectiveness. Certain EPS have immunomodulatory qualities that control the body's immunological response. These EPS can activate immune cells including dendritic cells and macrophages, which strengthens the host's defences and immunological responses to infections and malignancies. The creation of new immunotherapies and adjuvants for vaccines has a lot of potential as a result of EPS-induced immunomodulation (Singh et al. 2023).

The manipulation of EPS has major ramifications for biotechnology and environmental applications since they are crucial to the production of biofilms (Raj et al. 2023). EPS-producing bacteria can be genetically modified as part of biofilm engineering to modify the structure and functionality of the EPS matrix (Saadat et al. 2019; Morcillo and Manzanera 2021). This enables the development of biofilms with certain properties, such as improved adhesion, cohesiveness, or the capacity to break down particular contaminants. EPS help to create microbial biofilms, which are necessary for bioremediation procedures. EPS aid in the adherence and immobilisation of microbes that break down contaminants onto surfaces, increasing the efficiency with which they do so. Additionally, heavy metals and other harmful substances can be sequestered by EPS, which lessens their bioavailability and lessens their environmental effect (Behera et al. 2023). EPS have attracted interest as potential alternatives to plastics (biomedical plastics) made from petroleum. They provide desirable candidates for the creation of biodegradable materials, such as packaging films and coatings, because they are biodegradable and environmentally beneficial. Materials made of EPS can lessen the environmental damage caused by conventional plastics and support sustainable practises. It has been demonstrated that certain EPS generated by probiotic bacteria improves their survival and adherence to the intestinal mucosa (Nagrale et al. 2023). This enhances the probiotic bacteria's ability to promote gut health and general wellbeing. The management of digestive problems and preserving a healthy gut microbiome may be affected by EPS-mediated control of the gut microbiota (Kumari et al. 2023).

Application of exopolysaccharides in fabrication of dressings

Microbial EPS have shown promise as biomaterials for the creation of wound dressings with improved wound healing capabilities. These biopolymers are perfect for generating high-tech dressings that support tissue healing and regeneration, because they have a number of benefits, including biocompatibility, biodegradability, and the capacity to produce hydrogels (Kaur and Dey 2022). A Glycosaminoglycan-like EPS is produced by the Gram-positive bacteria Micrococcus luteus that mimics the glycosaminoglycans that are naturally present in the extracellular matrix of tissues. Dressings made from Micrococcus luteus EPS replicate the composition and characteristics of the natural extracellular matrix, making them the best choice for encouraging cell migration, adhesion, and tissue regeneration. It is well known that Acinetobacter spp. produce EPS that forms pellicle-like structures and aids in the development of bacterial biofilms (Shineh et al. 2023). When these biofilms are included in dressings, a protective environment that encourages wound healing is produced. Additionally possessing antibacterial qualities, the EPS from Acinetobacter species guard against bacterial colonisation and infection at the wound site (Hasan et al. 2023). Alginate is a well-known product of Pseudomonas aeruginosa and is a linear polysaccharide that creates a matrix that resembles gel. Alginate-based dressings offer a moist wound environment that aids in tissue repair and wound healing. The alginate matrix aids in the autolytic debridement of the wound, making it possible to remove necrotic tissue and speed up the healing process (Song et al. 2023).

Due to their high water content, softness, and biocompatibility, EPS hydrogels have drawn a lot of interest as wound dressings. EPS-based hydrogel dressings encourage wound wetness, improve cell migration, and stop wound dehydration (Nambiar et al. 2023). They are especially beneficial for accelerating the healing of dry wounds and persistent wounds. Because of their ability to stop bleeding and promote wound healing, alginate-based bandages made from Pseudomonas aeruginosa EPS or other alginate-producing bacteria are often utilised. When in contact with wound exudate, alginate dressings create a gel-like layer that fosters a moist environment for wound healing (Radhouani et al. 2023; Ghadimi et al. 2023). Dressings with EPS that have built-in bioactive qualities, such as immunomodulatory or antibacterial actions, can speed up the healing process of wounds. Dressings made with EPS from Micrococcus luteus, for instance, can boost the immune system and encourage tissue regeneration. To improve their mechanical qualities and potential for wound healing, several wound dressings blend EPS with additional substances like collagen or chitosan. EPS-producing bacteria and other biopolymers may be used in composite dressings to promote synergistic wound healing (Shahghasempour et al. 2023).

In order to take use of the characteristics of EPS and develop dressings with increased functionality for faster wound healing, a number of cutting-edge technologies are being used (Feketshane et al. 2022). Using casting processes, dressings are created by pouring an EPS solution onto a mould or substrate and letting it set up to adopt the shape that is needed. The fabrication of dressings with regulated thickness and porosity is made possible by this straightforward and economical technology (Remaggi et al. 2023). The mechanical characteristics and biodegradability of the dressings may be customised to fit certain wound types and healing phases by altering the concentration and mix of EPS solutions (Keshavarz et al. 2022). A flexible and effective method for creating nanofibrous dressings from EPS solutions is electro-spinning. In this procedure, an electric field is given to a polymer solution containing EPS, which triggers electrostatic forces that result in the creation of ultrafine fibres (Samyn et al. 2023). These nanofibers have a large surface area for cell adhesion and encourage cellular penetration into the dressing because they imitate the structure of the extracellular matrix. Electro-spun EPS dressings provide excellent moisture control and breathability, promoting a favourable environment for wound healing (Ruan et al. 2023). The ability to precisely manage the spatial arrangement and architectural design of EPS-based structures made possible by 3D printing has revolutionised the manufacture of dressings. The development of intricate, patient-specific dressings with specialised forms and functions is made possible by 3D printing technology (Mavrokefalou et al. 2023). The layer-by-layer deposition of EPS materials guarantees that the porosity and mechanical qualities may be adjusted to precisely suit the needs of different types of wounds. The addition of drug-delivery capabilities to 3D-printed EPS dressings allows for the prolonged and focused release of therapeutic drugs to speed up the healing of wounds. The flexible process of spray-drying may be utilised to turn EPS liquids into dry powder or micro-spherical dressings. In this method, an EPS solution is sprayed into a heated chamber in the form of a fine mist (Cruz-Santos et al. 2023). As the solvent quickly evaporates, dry EPS particles are left behind. These particles can be included in a variety of formulations, such as powders or gels for wounds that are simple to apply to the wound site. To increase their therapeutic efficacy, spray-dried EPS dressings can also be mixed with other bioactive substances, such as growth factors or antimicrobials (Kumar et al. 2023). Another technique for creating EPS-based dressings in a dry and stable state is freeze-drying, sometimes referred to as lyophilization (Elango et al. 2023). In this method, EPS solutions are frozen, and the ice is then sublimated away, leaving an EPS structure that resembles a porous sponge. Excellent rehydration qualities make freeze-dried EPS dressings a good choice for applications requiring quick absorption of wound exudate (Sethuram and Thomas 2023).

Exopolysaccharides in fabrication of surgical sutures

In order to recover properly after surgery and to seal wounds, sutures are a vital medical equipment. Sutures made from EPS provide special benefits such better biocompatibility, less tissue sensitivity, and better wound healing capabilities (Boateng and Catanzano 2015). The GAG-like EPS generated by Micrococcus luteus is one instance of microbial EPS used in the creation of sutures (de la Harpe et al. 2021). This EPS is ideally suited for uses in wound closure because it resembles glycosaminoglycans that are present in the extracellular matrix of tissues. Sutures contain GAG-like EPS that supports tissue regeneration by promoting cell adhesion and migration. Additionally, EPS-based sutures made from Micrococcus luteus show decreased inflammatory responses, which helps with post-operative healing and scarring reduction (Tirkey et al. 2023).

The alginate-based EPS made by Pseudomonas aeruginosa is another notable instance. A gel-like quality of alginate, a linear polysaccharide, makes it useful for sutures. When in contact with wound exudate, alginate-based sutures develop a protective gel-like coating, producing a moist environment that speeds up wound healing (Veerachamy et al. 2014; Edmiston et al. 2006). This property is especially helpful for wound dressings since it keeps the site from drying out and makes autolytic debridement easier, which helps remove necrotic tissue from the wound. Additionally, alginate-based sutures have built-in hemostatic qualities that lessen bleeding and offer additional advantages during surgery. The use of EPS generated by Acinetobacter spp. is one remarkable illustration. The production of bacterial biofilms is made possible by the EPS that Acinetobacter strains release, which forms pellicules. Researchers have developed sutures with improved wound healing powers by using the characteristics of Acinetobacter EPS. These biofilm-forming sutures offer a safe space at the wound site that lowers tissue inflammation and encourages cell growth. Furthermore, the EPS in these sutures has built-in antibacterial qualities that help prevent wound infections and promote healing (Raut et al. 2023). The inclusion of EPS from Bacillus spp. is a fascinating new use. EPS with distinct sticky characteristics is produced by Bacillus strains. Sutures' adhesive strength and retention at the wound site are enhanced by adding EPS made from Bacillus (Prasathkumar et al. 2023). With less chance of slippage or early deterioration, these sticky sutures provide superior wound closure. The adhesive qualities of EPS sutures made from Bacillus also aid in improving wound alignment, facilitating ideal wound healing, and reducing scarring. Furthermore, sutures with improved biocompatibility have been made using EPS from the cyanobacterium Nostoc commune. A mucilaginous sheath created by Nostoc commune EPS establishes a safe and biocompatible environment surrounding the bacterial colonies. Reduced tissue irritation and inflammation are seen in sutures made with Nostoc commune EPS, fostering a more favourable environment for wound healing. Patients with sensitive skin or a history of negative responses to traditional sutures will benefit most from these biocompatible sutures (Zainulabdeen et al. 2023).

Adhesive biomaterials including fibrin, chitosan, and dextran are suitable components for surgical sealants. The in situ gelling of dextran-chitosan shown outstanding adhesive qualities with little swelling and little cytotoxicity, according to research by Balakrishnan et al. The compatibility of the gels with cells was demonstrated by the gel composed of 5% ChitHCl and 10% DDA50, which preserved the usual spindle form of fibroblast cells in L929 mice. According to the results of the cytotoxicity tests, compared to cells not exposed to the substance extract, 95.8 ± 8.06% of cells were still metabolically active after 24 h. ChitHCl (5%) and DDA (10%) revealed metabolically active cells of 97.6 ± 7.12% and 102.3 ± 5.9%, respectively. Additionally, the study examined the dextran-chitosan composite's adhesive qualities and cytotoxicity in rabbits with wounded livers and discovered that it might function as an efficient sticky glue with little damage to cells (Balakrishnan et al. 2017). Sulfated levan, a form of bacterial EPS, has high biocompatibility and anticoagulant action, making it a promising candidate for use in cardiac tissue engineering. In a study, scientists combined sulfated levan with ALG (alginate), chitosan, and other ingredients to generate sticky free-standing multilayer films. The mechanical strength and adhesiveness of the produced adhesive films were greatly improved by the addition of sulfated levan. When the multilayer films were examined in vitro with the myoblast cell line C1C12, it was discovered that they were cytocompatible and myoconductive. These results highlight the sulfated levan-ALG-chitosan membrane's potential use in cardiac tissue engineering (Gomes et al. 2018).

Exopolysaccharides in fabrication of scaffolds

The use of bacteria as a natural scaffold to synthesise polymers on desired templates has been investigated in a number of research. Pins, wax, starch, agarose, and gelatin have all been used as templates for developing scaffolds, among other materials. Potential biomedical uses exist for these 3D designs, which were produced using printed bacterial constructs and pre-designed moulds.

For instance, Rambo et al. used Acetobacter xylinum to create porous, nanofibrous bacterial cellulose membranes. They used pin templates on a culture medium with sizes varying from 60 to 300 µm to create in-situ pores. When the templates were removed, the bacteria created a cellulose biofilm around the pins. This microporous structure could help with tissue regeneration, particularly when high oxygenation rates or a delay in wound contracture are needed (Rambo et al. 2008). Similar to this, by adding paraffin wax microspheres to the fermentation process with A. xylinum, Zaborowska et al. effectively created microporous bacterial cellulose scaffolds with pore sizes of 300–500 µm. A 3D porous scaffold was created after the wax microspheres had been eliminated. A 3D porous scaffold was created after the wax microspheres had been eliminated. This micro-porous scaffold is a viable contender for bone tissue engineering applications since the clustered cells within it encouraged denser mineral deposition (Zaborowska et al. 2010). A. xylinum was used in the fermentation procedure by Andersson et al. to create bacterial cellulose 3D scaffolds in the presence of wax particles (150–300 µm in diameter). They discovered that chondrocytes released glycosaminoglycan on the scaffold after extrusion, especially in regions where cells gathered together, indicating its potential utility in cartilage regeneration applications (Andersson et al. 2010). In a different work, Gluconacetobacter xylinus was grown to produce 3D micro-porous nanofibrous gelatin/bacterial cellulose scaffolds. In order to create macro-forms and manipulable microstructures, a gelatin template was employed. Cellulose nanostructures were created on the surface and within the 3D microporous scaffolds by synthesising the bacterial cellulose matrix into the micro-porous template. These scaffolds facilitated cell adhesion, proliferation, and maintenance of phenotypic characteristics while displaying outstanding biocompatibility. In addition to employing bacterial cellulose, microfluidic cellulose scaffolds with interconnected holes have also been created using agarose micro-particles (300–500 µm in diameter) as templates. A. xylinum cells were then grown through the developing pellicle. Following the autoclaving of the template, cellulose gels with interconnected networks of pores (diameters between 300 and 500 µm) were created. Compared to nonporous substrates, these scaffolds showed strong chondrocyte adhesion and growth with increased vitality. EPS from bacteria have been used in a number of methods to research the operations of microorganisms and build three-dimensional structures. For instance, agarose stamps made with various bacterial strains were utilised as a surface on which cells developed 'living stamps,' enabling the design of patterns and the investigation of microbial activities. In order to immobilise cells and create 3D printed structures, a printing technology known as “Flink” was created employing cell-filled hydrogels and biocompatible components including k-carrageenan, hyaluronic acid, and fumed silica. To create cellulose 3D structures that might be employed in areas subject to mechanical strain, including the elbow and knee, these hydrogels were loaded with A. xylinum (Faria et al. 2022). Additionally, Rühs et al. foamed a mannitol-based medium with a bacterial suspension of G. xylinus to create a porous bacterial cellulose foam. They utilised xanthan to stop water drainage and cremodan as a surfactant to stabilise air bubbles. In order to solve the lack of porosity in traditionally manufactured bacterial cellulose, the bacteria developed cellulose biofilms at the interface between the culture medium and the gas phase. This created biocompatible 3D structures ideal for tissue engineering and wound healing (Rühs et al. 2018).

Exopolysaccharides in drug delivery

EPS have a variety of functional groups in their chemical structure, including hydroxyl, amino, and carboxylic acid groups. EPS are highly changeable due to their complex functional groups, which enable modifications to their chemical structure or the addition of new groups, which can improve or develop new biological functions (Paul et al. 2023). The biodistribution of drug molecules transported by EPS throughout the body is significantly impacted by the structural changes of EPS (Hooshdar et al. 2020). Additionally, various EPS characteristics can result in various drug delivery systems' (DDS) targeting capabilities. EPS are advantageous as DDS carrier materials because they include key DDS characteristics, such as biocompatibility and biodegradability, which allow them to correctly transport medications to certain tissues and organs at the right moment (Zayed et al. 2022). Additionally, EPS high natural content and affordable processing offer certain benefits for their usage as carrier materials. The potential for medical uses of microbial EPS, such as hyaluronic acid, chitosan, glucan, and pullulan, has been made possible by recent research (Bagnol et al. 2022). Because of their smaller molecular weight, better purification yield, and more stable structure, microbial EPS provide benefits over the animal and plant EPS that are frequently employed in DDS. Microbial EPS can improve the efficacy of medication activities, produce better therapeutic outcomes, and lower costs when used as drug carriers. The investigation and development of microbial EPS drug carriers has emerged as a significant scientific trend (Santra and Banerjee 2021).

Excellent adhesion capabilities of microbial EPS have been shown to increase drug bioavailability by lowering drug excretion and extending drug circulation in the body (Krishnaswamy and Lakshmanaperumalsamy 2021). Microbial EPS can be coupled with pharmaceuticals to generate conjugates that have longer residence times and better control over drug effects, which can help counteract the bloodstream's quick fall in free drug concentration. Additionally, by loosening the tight connections between epithelial cells, certain cationic EPS, including chitosan and its derivatives, might increase the permeability of hydrophilic medicines (Sharifian and Homaei 2022). Since microbial EPS structures have a variety of chemical groups, it is possible to attach various ligands to the particle surface and target specific tissue regions. Microbial EPS have been successful in the creation of innovative drug delivery systems, such as mucosal, transdermal, and ocular DDS, which offer benefits including avoiding the liver and having less hazardous side effects (Debnath et al. 2021). It is now well-established that microbial EPS film production is used in medication release. Notably, microbial EPS are used in targeted delivery of low molecular weight pharmaceuticals as well as drug delivery studies for nucleic acid drugs, protein therapy, controlled and local delivery gel, and nanostructures for eye treatment drugs (Villarreal-Otalvaro and Coburn 2021). Because of this, microbial EPS are excellent candidates for use as drug carriers in biologic drug delivery systems, such as those used to administer vaccinations, cure viral infections, and treat cancer (Jurášková et al. 2022). Microbial EPS-based DDS has several benefits, but there are certain formulation drawbacks, including susceptibility to microbial contamination, uncontrollable hydration rates, and decreased viscosity during storage. Further study is necessary to address these issues and comprehend the processes underlying medication release and osmotic increase of microbial EPS (Stoica et al. 2023).

Pathogenic bacterial growth was inhibited by the EPS isolated from Ochrobactrum pseudintermedium C1. It had much more effective antibacterial action when paired with the antibiotic ciprofloxacin, indicating its potential as an adjuvant to stop antibiotic resistance (Razzaghi et al. 2021). More powerful bactericidal action was shown by gold nanoparticles functionalized with bacterial EPS than by EPS alone. According to in vitro and in vivo investigations, the bacterial compound EPS curdlan also demonstrated the capacity to prevent Mycobacterium tuberculosis (Mtb) from growing. Nitric oxide generation caused by curdlan treatment stimulated macrophage activation in Mtb-infected mice. Peripheral blood mononuclear cells were encouraged to produce cytokines by EPS produced from Bifidobacterium longum W11 (Laubach et al. 2021). EPS from a specific strain of Lactobacillus showed strong immunomodulatory and antioxidant properties. By chelating ferrous ions, preventing lipid peroxidation, scavenging radicals, and having a reducing capability, they showed antioxidant properties (Priyanka et al. 2024). Aside from having bioactive qualities, bacterial EPS has the potential to be a useful drug delivery system for anticancer medications and growth hormones. With antibiotics in particular, bacterial EPS has been used as a model for drug delivery release. To protect ciprofloxacin from gastrointestinal conditions in vitro, kefiran-ALG microspheres, for instance, were created to permit regulated release of the drug (Kalimuthu et al. 2023). To demonstrate cytocompatibility in vitro with human lens epithelial cell culture and in vivo with rabbit models, succinic anhydride-modified xanthan gel enabled the prolonged release of gentamicin under physiological circumstances (Daba et al. 2021). Bacterial cellulose has potential as a replacement for plant-based materials in dental and medical applications due to its high tensile strength, absorption, and biocompatibility (Gentry et al. 2023). According to a study by Inoue et al. (2020) bacterial cellulose was utilised to release chlorhexidine up to 10 times more efficiently than unmodified cellulose, demonstrating how it has been employed to produce extended drug release. Through the use of a microfluidic technique, TGF-β1, a growth factor for cartilage regeneration, was added to EPS-based microparticles. According to in vitro experiments, this tactic successfully increased the bioactivity and bioavailability of TGF-β1. Epirubicin, an anticancer medication, was found to extend drug retention and improve its antitumor potential in vivo in a different investigation using EPS-based microparticles. When compared to a cellulose membrane devoid of the angiogenesis-promoting substance vaccarin, a wound healing membrane produced from bacterial cellulose loaded with vaccarin demonstrated enhanced physical and mechanical qualities. Both vaccarin-loaded and natural cellulose membranes passed the in vitro test using mouse fibroblast cells, L929. In animal investigations using ICR male mice, the cellulose membrane loaded with vaccarin, however, showed a superior healing effect than the membrane unloaded with vaccarin, encouraging neovascularization and epithelization in the skin-wounded mouse models (Inoue et al. 2020).

Exopolysaccharides as coating agents

Mechanically stable metals or polymers are frequently used in medical equipment to increase their durability and eliminate the need for repeated procedures. However, using hard materials may trigger immunological reactions that might be harmful. EPS, in particular dextran, have been used as coating materials to solve this problem and enhance the biocompatibility of medical devices (Goswami et al. 2022). Dextran was studied by Kil et al. (2019) for use as a coating for brain probes. They discovered that the dextran's stiffness and rate of deterioration could be controlled by varying the molecular weight and coating thickness. After 4 months after implantation using a dextran-coated neural probe, they found that scar tissue development in their investigation using Wistar rats was negligible. As the implant location was approached, there was no discernible decrease in the number of viable neurons around. Vascular endothelial growth factor (VEGF) has showed promise in recruiting endothelial cells to attach to vascular implants in vascular grafts, potentially increasing vascular regeneration (Kil et al. 2019). Even though metals like titanium are often used for bone implants, understanding their corrosion behaviour is still difficult. According to Saveleva et al. (2019) organic polymers like dextran can be used to coat a titanium-based implant to increase its corrosion resistance against simulated bodily fluid (Saveleva et al. 2019).

Biomedical potential and activities of exopolysaccharides

Immunomodulatory potential

Innate and adaptive immunity make up the immune system, which cooperates to defend against dangerous intruders. The impact of EPS on the immune system's signalling pathways has been investigated (Fig. 2). The potential immunomodulatory effects of a variety of dietary sources, including algae, plants, mushrooms, and probiotics, have been well investigated. Through a variety of processes, including stimulating the formation of ROS and NO (nitric oxide) and raising the release of cytokines like IL-6 and TNF-α, EPS can modify the immune response (Chen et al. 2019). EPS have been investigated for possible usage against viruses like SARSCoV-2 due to their propensity to modulate the immune system. Numerous in vitro and in vivo research have looked at how dietary EPS affect the immune system (Vázquez et al. 2021). For instance, zebrafish and the cell line (RAW264.7) both displayed enhanced phagocytosis, nitric oxide, and cytokine production in response to SRP70-1, a EPS from Stevia rebaudiana. The Lactobacillus kefiranofaciens-produced kefiran showed immunomodulatory effects on the intestinal mucosa and potential therapeutic value for intestinal diseases. Additionally, β-glucans from edible fungi like mushrooms and yeasts have demonstrated immunomodulatory effects through affecting different immunological reactions. Yeast particle β-glucans stimulated dendritic cells and macrophages, triggering an immune response that is anticancer. Additionally, -glucan from the fungus Pleurotus eryngii elevated cellular levels of TNF-α, IL-1, and IL-6, enhanced NF-κB and TLR signalling gene expression, and activated the β-glucan receptor dectin-2, indicating immunological activation via the β-glucan receptor dectin-2-Syk-(CARD9/Bcl-10/MALT1) pathway. Furthermore, polysaccharides from the peel of Citrus reticulate from varied storage durations have enhanced RAW264.7 cells' survival and raised NO generation in a dose-dependent manner. The immunomodulatory properties of several mushrooms, including Agaricus brasilensis and A. bitorquis, have also been recognised (Dedhia et al. 2022).

Fig. 2.

Various types of immune response induced by microbial EPS (Modified using Biorender.com)

Anti-oxidative efficacy

EPS antioxidant effects principally result from their capacity to scavenge free radicals (Fig. 3). Additionally, they can influence cellular antioxidant enzymes including catalase, superoxide dismutase, peroxidase, and glutathione peroxidase to provide antioxidant effects. Food polysaccharides' antioxidant properties vary depending on their molecular weight, uronic acid concentration, and component monosaccharides (Gezginç et al. 2022). For instance, OPP-D's high nonmethylated galacturonic acid concentration may be responsible for the substance's comparatively strong antioxidant activity. Researchers have expressed interest in examining the antioxidant capacity of certain edible mushrooms. Multiple in vitro tests, such as DPPH, FRAP, hydroxyl radical scavenging, superoxide radical scavenging, copper reducing antioxidant power, Fe²⁺ chelating activity, and lipid peroxidation inhibitory activity were used in studies to examine antioxidant activity (Choi et al. 2021). With EC₅₀ values ranging between 1.08 and 4.91 mg/mL, Pleurotus eous polysaccharide (PEPA-1a) from the edible fungus Pleurotus eous revealed strong antioxidant activity in several experiments (Gunasekaran et al. 2021). Another study investigated the antioxidant activity of a polysaccharide made of β-glucan from the Russuloid macrofungus "Jam Patra," which was discovered in West Bengal, India. With EC50 values ranging from 305 to 2726 g/mL, this polysaccharide demonstrated antioxidant activity in tests for reducing power, chelating ability, and radical scavenging. Popular polysaccharides from Lentinus edodes, P. eryngii, and P. djamor also showed potential antioxidant action. Exopolysaccharides from probiotic sources have also demonstrated antioxidant activity, suggesting a potential use in improving cellular health (Dedhia et al. 2022).

Fig. 3.

Illustration demonstrating various sources of ROS production in cell and inhibition of ROS by microbial exopolysaccharides (NADPH-Nicotinamide Adenine Dinucleotide Phosphate Hydrogen) (Created using Biorender.com)

Neuroprotective activity

Due to the ageing population, neurodegenerative illnesses including Alzheimer's, Parkinson's, and multiple sclerosis are a major public health problem (Ge et al. 2022). There has been a lot of interest in the creation of neuroprotective drugs that can stop or postpone neurodegeneration (Chaturvedi and Chakraborty 2021). Exopolysaccharides (EPS) produced by microorganisms have recently come to light as possible candidates with promising neuroprotective qualities. High-molecular-weight polysaccharides known as EPS are released by a variety of microorganisms, such as bacteria, fungus, and algae (Sirin and Aslim 2021). The antioxidant activity of microbial EPS is one of their main mechanisms (Fig. 4). Oxidative stress, which results in the buildup of reactive oxygen species (ROS) and subsequent damage to neurons, is frequently linked to neurodegenerative disorders (Wang et al. 2023b). EPS are effective free radical scavengers that reduce ROS and guard against oxidative stress on neural cells. EPS from a variety of sources, including bacterial EPS from Bacillus subtilis and fungal EPS from Ganoderma lucidum, have been used to demonstrate this characteristic. The anti-inflammatory properties of microbial EPS are another significant factor. A major factor in the development of neurodegenerative disorders is chronic inflammation. Microbial EPS have anti-inflammatory qualities that serve to temper astrocyte and microglial activation, hence lowering the production of pro-inflammatory cytokines (Jiang et al. 2022).

Fig. 4.

Mechanistic pathway demonstrating neuroprotective effects of microbial exopolysaccharide via its anti-oxidative potency (TrkB-Tropomyosin Receptor Kinase B; P-Phosphate; Akt-Protein Kinase B; Nrf2-Nuclear Factor Erythroid-2 related Factor; HO-1-Heme Oxygenase-1; GCLC-Glutamate Cysteine Ligase Catalytic Subunit; NQO-1-NAD(P)H Quinone Oxidoreductase) (Created using Biorender.com)

By encouraging the synthesis of neurotrophic factors including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), EPS can also offer neurotrophic assistance (Dhahri et al. 2021). These elements support synaptic plasticity, neuronal development, and survival. It has been demonstrated that the bacterial EPS from Bifidobacterium breve increases BDNF expression in cultured cortical neurons. Furthermore, gut microbiota composition can be impacted by microbial EPS, resulting in the formation of compounds having neuroprotective effects. Through the gut–brain axis, the gut bacteria interacts in both directions with the central nervous system. This axis may be modulated by microbial EPS, which may have an effect on the health of the neurons. For instance, the generation of short-chain fatty acids, which have been linked to neuroprotection, was boosted by EPS from Lactobacillus helveticus. For its capacity to protect neurons, the medicinal fungus Ganoderma lucidum has been the subject of intensive research. Its EPS have demonstrable anti-inflammatory and antioxidant properties that shield neurons from oxidative damage. According to studies, G. lucidum EPS may have therapeutic advantages in the treatment of neurological illnesses. A probiotic bacteria renowned for improving gut health is Lactobacillus fermentum. In animal models of dementia, its EPS have shown neuroprotective benefits by lowering neuroinflammation and boosting neuronal survival. A blue-green algae known as Spirulina platensis has a number of health advantages. Its EPS were demonstrated to shield neurons against amyloid-beta peptide-induced oxidative stress and apoptosis, two symptoms that are characteristic of Alzheimer's disease (Selim et al. 2023).

Cardioprotective activity

Cardiovascular diseases (CVD) are the main cause of mortality worldwide, causing more deaths each year than any other condition. Polysaccharides are helpful in preventing cardiovascular disease (CVD). Their capacity to reduce total triglycerides and lipids, as well as their anti-coagulative and anti-aggregating effects on blood platelets, are all credited with contributing to their cardioprotective efficacy (Fig. 5). Despite the fact that fewer research than for other biological processes have examined polysaccharides' cardioprotective properties, the results from these studies are important. Reduced cholesterol absorption and increased bile acid excretion are the major ways that the cardioprotective effect is accomplished. Additionally, intestinal bacteria digest polysaccharides, resulting in the creation of short-chain fatty acids (SCFA) such acetic acid, propionic acid, and butyric acid, which block the biosynthesis of cholesterol. Mushroom polysaccharides have also demonstrated cardioprotective properties by reducing hyperlipidemia (Nikolic et al. 2023). Similar to this, sulfated polysaccharides from the edible sea algae Padina tetrastromatica (50 mg/kg BW) normalised oxidative damage, hyperlipidemia, endothelial dysfunction, and inflammatory responses in male Sprague–Dawley rats with isoproterenol-induced myocardial infarction. When taken as a control, the conventional medication aspirin had similar effects to those seen. According to the findings, these polysaccharides' cardioprotective effects were due to their anti-inflammatory and hypolipidemic properties (Lekshmi and Kurup 2019).

Fig. 5.

Cardioprotective effects of microbial exopolysaccharide on atherosclerosis (blood vessel view on treatment progression) (Modified using Biorender.com)

Anti-cancer potential

EPS from microorganisms have demonstrated positive anti-cancer properties and are now being considered as viable treatments and preventative measures for cancer (Marimuthu and Rajendran 2023). High-molecular-weight polysaccharides known as EPS are released by a variety of microorganisms, such as bacteria, fungus, and algae. Their capacity to regulate several cellular processes, restrain the development of tumours, and boost the immune response against cancer cells are all ascribed to their anti-cancer capabilities (Fig. 6) (Salimi and Farrokh 2023). Researchers have looked at the anti-cancer properties of EPS derived from several microbial sources. For instance, EPS generated by Lactobacillus plantarum has proven to have anti-tumor effect by causing cancer cells to undergo apoptosis, or programmed cell death. Additionally, it has been demonstrated that EPS from Bifidobacterium longum can slow the development of tumour cells and encourage the arrest of the cell cycle in cancerous cells (Zhang et al. 2023d). Their capacity to control the immune system is one of the main ways that microbial EPS perform anti-cancer actions. A key component of the body's defence against cancer is the creation of immune-stimulating chemicals like interferons and interleukins, which EPS can increase. Additionally, EPS can stimulate immune cells, such as T cells and natural killer cells, which hunt down and kill cancer cells. It has been noted that EPS produced from Pseudomonas aeruginosa and Rhizopus nigricans have this immune-stimulating activity (Zhang et al. 2023b). Additionally, angiogenesis—a process essential for the development and spread of tumors—can be hampered by microbial EPS. Angiogenesis is the process by which new blood vessels emerge. The angiogenesis-inhibiting properties of EPS from Ganoderma lucidum have been demonstrated to restrict the blood supply to tumours and hinder their growth (Chen et al. 2023). Several marine bacterial EPS from species like Lactobacillus delbrueckii and Bacillus velezensis have also been investigated for its anti-cancerous activities (Jeewon et al. 2023).

Fig. 6.

Anti-cancer potential of microbial exopolysaccharide through immune stimulation (EPS-Exopolysaccharides; IFNγ-Interferon gamma; IL-1β-Interleukin 1-Beta; TNF-Tumor necrosis factor) (Created using Biorender.com)

The capacity of microbial EPS to scavenge free radicals and lessen oxidative stress is another crucial anti-cancer activity (Arayes et al. 2023; Chirakkara and Abraham 2023). Due to their high metabolic activity, cancer cells frequently experience elevated oxidative stress. Strong antioxidants, EPS may disarm free radicals and guard healthy cells from harm. EPS from Lactobacillus fermentum and Streptococcus thermophilus have shown antioxidant activity and may be able to shield cells from oxidative stress-related carcinogenesis. Additionally, microbial EPS can stop cancer cells from adhering to things and invading other tissues. One of the main causes of cancer-related fatalities is metastasis, which is the spread of cancer cells to different regions of the body (Chirakkara and Abraham 2023). Cancer cells' capacity to adhere to the extracellular matrix has been found to be inhibited by EPS from Lactobacillus acidophilus, potentially decreasing their invasion potential. Microbial EPS can improve the effectiveness of traditional cancer therapies in addition to having direct anti-cancer effects. According to studies, the radiation therapy can be made more successful by making cancer cells more sensitive to EPS from Bifidobacterium animalis subsp. lactis. A few chemotherapy medicines have been shown to have increased anti-cancer efficacy when combined with EPS from Streptococcus thermophilus (Tregubova et al. 2023).

Anti-diabetic potential

2.8% of the world's population now has diabetes mellitus (DM), and by 2030, it is anticipated that 439 million people would have the disease. Current diabetic therapies frequently include synthetic chemicals, which can have serious adverse effects and potentially harm organs in those with chronic DM (Kumar et al. 2022). As a result, to address the treatment of DM, researchers are now concentrating on looking into complementary and natural anti-diabetic medicines. Microbial polysaccharides, one of these substitutes, have demonstrated excellent results in lowering blood glucose levels, making them possible options for treating diabetes (Kaveh et al. 2023).

Researchers have focused on inhibiting digestive enzymes like α-glycosidase and α-amylase in their search for potent anti-diabetic drugs by examining how microbial polysaccharides interact with these enzymes (Muninathan et al. 2022). By inhibiting these enzymes, blood glucose management is enhanced because less glucose is absorbed from carbohydrates in the intestines. Researchers have also looked at how microbial polysaccharides affect the absorption of insulin in insulin-resistant cell lines (Kavitake et al. 2022). This strategy seeks to improve the cells' receptivity to insulin, which is crucial for controlling diabetes (Fig. 7). Additionally, animal models such as Sprague–Dawley rats, Kunming mice, and KK-Ay mice have been used to research how microbial polysaccharides affect blood sugar levels. These animal studies offer important information on the possible anti-diabetic activities of microbial polysaccharides in living creatures, assisting researchers in understanding how these substances can affect diabetes conditions (Shori and Baba 2023).

Fig. 7.

Anti-diabetic effect of microbial exopolysaccharide through stimulating the increment in insulin absorption (IR-Insulin Receptor; IRS-Insulin receptor substrate; P13K-phosphoinositide-3 kinase; PDK1/2-Phosphoinositide dependent kinase-1/2; P-Phosphate; Akt-Protein kinase B; GrK3-Glycogen synthase kinase-3; GS-Glycogen synthase; ERK-Extracellular signal regulated kinase; MAPK-Mitogen activated protein kinases; GLUT4-Glucose transporter type-4) (Created using Biorender.com)

Safety evaluation of microbial exopolysaccharides

A critical component of the use of microbial EPS in a variety of sectors, such as food, medicine, and cosmetics, is the examination of their safety. The safety of these polysaccharides for human ingestion and other possible purposes is thoroughly evaluated prior to their usage as additives or active substances.

Toxicological research is first carried out to identify any potential negative effects of microbial EPS. In these experiments, test subjects—typically animals—are exposed to various polysaccharide concentrations for a predetermined amount of time. Toxicological indicators including variations in behaviour, organ function, or histopathological changes are observed and evaluated. In order to provide crucial safety reference points, it is intended to determine the No Observed Adverse Effect Level (NOAEL) and the Lowest Observed Adverse Effect Level (LOAEL) for the polysaccharides (Chauhan and Sharma 2023). To evaluate the immediate negative effects of large dosages of the polysaccharides, acute toxicity studies are also carried out. These assessments are crucial in figuring out the safe dose ranges for human usage. To find any allergic reactions that could be brought on by microbial EPS, examinations of possible allergenicity and sensitization are also carried out. In vitro experiments examine the ability of the polysaccharides to generate allergic reactions, whereas skin patch tests are frequently used to measure sensitization. Since allergic responses to food additives or cosmetic components might have serious effects for certain people, it is crucial to conduct a comprehensive investigation into these issues. It is possible to give customers with the right labelling and warnings to help them avoid having a bad response by detecting any allergenic characteristics (Jin et al. 2023).

Microbial EPS are evaluated for their genotoxicity and mutagenicity in addition to toxicological and allergenicity tests. These investigations seek to determine if the polysaccharides can alter cellular genetics or result in mutations. Genotoxicity testing include chromosomal aberration assays utilising animal models and in vitro experiments to find DNA damage (Xue et al. 2023). The results of these analyses are essential for assuring the long-term safety of microbial EPS and reducing the possibility of any potential carcinogenic consequences. Overall, a thorough and organised process is used to evaluate the safety of microbial EPS in order to determine any potential negative impacts on people and the environment (Nachtigall et al. 2023). Researchers can identify the safe dose levels, possible allergic responses, and genetic effects of these polysaccharides by thorough toxicological studies, assessments of allergenicity, and investigations into genotoxicity. The industrial uses of microbial EPS can be maximised while preserving consumer health and safety by adhering to strict safety regulations (Asianezhad et al. 2023).

Future recommendations and perspectives

Future suggestions and perspectives for their use are intriguing and interesting, and microbial EPS show great promise for a variety of applications. First, further research and development should concentrate on discovering fresh microbial sources and improving exopolysaccharide manufacturing methods (Hosken et al. 2023). Different microbial strains might have different characteristics and produce polysaccharides with various functions. Researchers can find novel EPS with useful properties for a variety of businesses by studying fewer well-known bacteria (Shetty et al. 2023). To improve the effectiveness of polysaccharide production, biotechnology and fermentation methods developments should also be pursued. This entails investigating affordable substrates, perfecting the fermentation process, and increasing output to satisfy market demands. The manufacturing costs will ultimately be reduced, increasing the viability of microbial EPS as a commercial product (Sun et al. 2023).

Second, there is a rising preference for natural and healthy components in the food and pharmaceutical industries (Monteiro et al. 2023). EPS produced by microorganisms are a great replacement for synthetic additives since they are biodegradable, non-toxic, and have a variety of positive health effects. The potential of these polysaccharides as functional dietary components or as natural additions in medicinal formulations should be explored in future study (Iqbal et al. 2023). Furthermore, research examining the prebiotic qualities of microbial EPS may clarify their function in enhancing gut health and regulating the gut microbiota. These polysaccharides may play a significant role in the creation of functional foods and nutraceuticals by proving their efficacy and safety. Thirdly, more research should be done to determine the potential of microbial EPS in environmental applications (Pattnaik et al. 2023). These polysaccharides are useful in wastewater treatment and environmental remediation since they have been shown to exhibit features such heavy metal sequestration, biodegradation, and anti-biofilm action. The goal of ongoing research should be to maximise their usage in various applications, opening the door for sustainable and eco-friendly answers to environmental problems (Agrawal et al. 2023).

Furthermore, the application of microbial EPS in nanotechnology is quite promising. These polysaccharides can serve as stabilisers, encapsulating agents, or carriers for nanoparticles because of their distinct physicochemical characteristics (Kaur et al. 2023). This creates possibilities for innovative nanocomposite materials with a variety of functions, increased bioavailability of medicines, and tailored drug delivery systems. To create novel materials and medication delivery systems, researchers should investigate the possibilities of merging microbial EPS with nanotechnology. Efforts should be undertaken to increase industry and regulatory body understanding of the potential advantages and safety profiles of microbial EPS in order to promote wider utilisation of these compounds (Debbarma et al. 2023). The creation of policies and standards for the use of these polysaccharides in diverse applications will be made easier by cooperative efforts between regulatory agencies, business, and academia. These initiatives will encourage the wider use of microbial EPS and serve to increase public confidence in their safety and effectiveness (Gupta and Tamrakar 2023).

Conclusion

The commercialization of microbial EPS offers a promising path for the creation of a wide range of applications in a variety of fields. Food and beverage, pharmaceuticals, cosmetics, and biotechnology industries all stand to benefit greatly from the distinctive physicochemical characteristics and wide range of capabilities of EPS. The production of EPS may be improved by creative bioprocessing methods and developments in microbial engineering, leading to affordable and sustainable alternatives. These biopolymers are very desirable for the creation of innovative products due to their multifunctionality, which includes their emulsifying, gelling, and stabilising capabilities, as well as their bioactivity and biocompatibility. It is clear that these microbial EPS offer considerable potential for addressing societal demands and encouraging developments in numerous industrial sectors as research continues to identify novel EPS sources and utilise their diverse uses. However, further research is needed to uncover their full potential and address issues like large-scale production and regulatory barriers, opening the door for their integration into daily life and spurring innovation across a range of sectors.

Author contributions

NSK and CY: original draft, methodology, data curation; editing; SS and BGP: conceptualization, formal analysis; validation; visualization; review and editing.

Data availability

The data and the materials are all available in this article.

Declarations

Conflict of interest

The authors declare that there is no conflict of interest.

Informed consent

Not applicable.

Research involving human participants and/or animals

This work does not involve any human or animals participants.